<html>
<head>
    <style>
        .README{
            background-color: cadetblue;
            color: white;
            margin-left: 200px;
            margin-right: 200px;
            padding: 10px;
        }
    </style>
</head>
<body>
<h3>This is a header</h3>
<p>This is a paragraph.</p>

<!-- 块级元素，定义文档中的分区/节 -->
<div style="color:#ffffff;background-color: black;">
    <h3>This is a header</h3>
    <p>This is a paragraph.</p>
</div>
<br />

<!-- 类，使得该类的元素被CSS定制样式-->
<div class="README">
    <h1 style="text-align: center;">README</h1>
    <p style="text-align: center;">Welcome to my Blog!</p>
    <p style="text-align: center;">Hello World</p>
</div>
<br />

<div class="README">
    <h1 style="text-align:center;color: #ffffff;"> SouthBegonia</h1>
</div>

</body>
</html>